Ask A Vet: How Do I Introduce Our New Kitten to an Older, Aggressive Cat?


Welcome to our weekly 'Ask a Vet from the SF SPCA' feature on Dr. Jeannine Berger, DVM, DACVB is a board certified veterinary behaviorist who counsels guardians whose pets’ issues are beyond the scope of training. Think of her as a pet shrink…at your service. Ask your own questions in the comments!

Q: My cat has had an aggression problem since I took her in as a stray in 2000. I thought now that she's older (about 16), she might be over it. We adopted a kitten for my daughter's birthday, went through a slow introduction process, and thought it was working. But then the older cat's switch flipped and she cornered and attacked the kitten. The kitten is fine, but now we're living with closed doors, moving cats around, etc. How can we help the situation?

A: Thanks for reaching out to us. Adding a new kitten to a household can be challenging, especially if the resident cat is an older one. There can be many reasons for aggression in household cats and each case needs to be evaluated carefully to make the best individualized treatment plan. I strongly encourage you to make an appointment with us, however, until the situation in your home can be properly assessed, I strongly recommend to keep the older cat as comfortable as possible. Chronic stress in an older cat can cause serious health issues.

Here is my stop-gap advice until a behaviorist can thoroughly assess the situation: Keep the cats completely separate from one another. Make sure that each cat is comfortable in its own area, each with at least one litterbox, resting areas, food, and water, and that they receive equal amounts of attention. If the older cat can handle it, you can periodically switch the rooms that the cats are in so that they may smell the other cat without the potential for a fight to occur. It is important to prevent them from interacting negatively with each other. The more that they display aggressive behavior, the more they continue to relearn it and potentially worsen this behavior. Such signs of aggression include hissing, growling, swatting, stalking, and can even be as subtle as staring at each other. Guarding resources, such as sitting, standing or patrolling in front of litter boxes, food dishes, and entrances/exits are other displays of problematic behavior.

You'll want to assure that all of the interactions between your cats are positive. You can achieve this by gradually reintroducing the cats to each other during short and controlled sessions. Once they are calm and comfortable in each other’s presence during controlled sessions, you can begin to allow them to interact with each other under less structured circumstances, but still under close supervision.

Always be prepared to reward positive interactions. Provide your cats with plenty of opportunities to get away from each other. You can add vertical space for them to climb up and away from each other, if they choose. Some ways to do this are: Adding cat trees, providing access to cleared-out areas in bookshelves or tables, etc.

Not to toot our own horn, but the San Francisco SPCA offers a unique service in the behavior field. We have, on staff, one of the country's few Board Certified Behaviorists, who happens to be me. After an initial consultation, we will come up with an in-depth treatment plan. It may involve medications. Most importantly, we will identify if your older cat has an existing health problem that could be causing the sudden aggression. If you are interested, here is more information on our services.

Good luck with your cats.

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